1. Field of the Invention
The present invention relates to a light-emitting device and a fabrication method thereof, and more particularly to a light-emitting diode and a fabrication method thereof.
2. Description of the Related Art
With reference to FIG. 1, which is a schematic cross-sectional view showing the structure of a conventional light-emitting diode device. The light-emitting diode device 1 includes a substrate 10, a buffer layer 11 on the substrate 10, a first confining layer 12 on the buffer layer 11, an active layer 13 on the first confining layer 12, a second confining layer 14 on the active layer 13, a contact layer 15 on the second confining layer 14, a transparent electrically conductive layer 16 on the contact layer 15 and a set of electrode units 17. The set of electrode units 17 is comprised of a first electrode 17a located on the first confining layer 12 and a second electrode 17b located on the transparent electrically conductive layer 16, which work in coordination to provide the light-emitting diode device 1 with electric energy.
For the above-mentioned structure, the first confining layer 12 has a type of electrically conductivity different from that of the second confining layer 14. For example, the first confining layer 12 and the second confining layer 14 are made of n-type doped and p-type doped gallium nitride (GaN) semiconductor materials, respectively.
The first and second electrodes 17a and 17b of the set of electrode units 17 are made of metals such as gold, chromium and/or the alloy thereof. The first electrode 17a is arranged on the n-typed first confining layer 12, and an ohmic contact therebetween is formed, while the second electrode 17b is arranged on the top face of the transparent electrically conductive layer 16, and an ohmic contact thereof is formed with the contact layer 15, so as to provide the n-typed first confining layer 12 and the p-typed second confining layer 14 with electric energy.
While the electric energy is applied to the light-emitting diode device 1 through the first and second electrodes 17a and 17b, the current will pass through the n-typed first confining layer 12 and the p-typed second confining layer 14. The current flowing from the second electrode 17b into the light-emitting diode device 1 is uniformly distributed whereby the electron and the hole are combined within the active layer 13 so that the energy is released and converted into light energy for light-emitting. The active layer 13 has a structure of multi-quantum wells including a plurality of barrier layers 13a and plural layers of quantum well 13b which are stacked on each other.
In order to enhance the light-extraction efficiency of the light-emitting diode device 1, the p-typed second confining layer 14 and the contact layer 15 are patterned to form a plurality of openings therein, so as to enable a sufficient contact of the second electrode 17b with the p-typed second confining layer 14 and the contact layer 15. In this case, the lighting brightness of the light-emitting diode device 1 can be increased.
Nevertheless, the working voltage of the patterned p-typed second confining layer 14 is relatively increased as well. In view of this, an improved structure for the light-emitting diode device and the fabrication method thereof are provided in the present invention, by which not only the issue relating to the increased working voltage is addressed but the fabrication process therefor is simplified and the product cost thereof is reduced.